A couple covered with the US and the pride flags pay their tribute for the victims of a 12 June mass shooting in Orlando, Florida, USA, as they look at the Eiffel tower, illuminated in rainbow colours, in Paris, France, 13 June 2016. A total of 50 people including the suspect were killed and 53 were injured in a shooting attack at an LGBT club in Orlando, Florida, in the early hours of 12 June. The shooter was killed in an exchange of fire with the police after taking hostages at the club. (Photo by Yoan Valat/EPA)

In this photo taken on Sunday, January 14, 2018, Anastasia Gruzdeva, left, poses for selfie with her friends as the temperature dropped to about –50 degrees (–58 degrees Fahrenheit) in Yakutsk, Russia. Temperatures in the remote, diamond-rich Russian region of Yakutia have dropped to near-record lows, plunging to –67 degrees Centigrade (-88.6 degrees Fahrenheit) in some areas. (Photo by Sakhalife.ru Photo via AP Photo)

The National Geographic Photo Ark is a travelling exhibition of photographer Joel Sartore’s quest to create a photo archive of biodiversity around the world. So far, Sartore has captured studio portraits of more than 6,000 species – a number that he hopes to double. On 1 July, the ark will open at Melbourne zoo – the first time it has been exhibited in the southern hemisphere. More than 50 portraits will be on display, including many of Australian endangered animals being protected by programs at the zoo itself. These captions have been edited from text supplied by Melbourne zoo. Here: Barking owl. (Photo by Joel Sartore/National Geographic Photo Ark/The Guardian)

A chicken seller carries his chickens on his head in the market in Peshawar, Pakistan, August 20, 2015. (Photo by Khuram Parvez/Reuters)

A migrant boy sits on railway tracks at a train station in Tovarnik, Croatia, September 20, 2015. (Photo by Antonio Bronic/Reuters)

A US Marine leads two Viet Cong suspects in restraints during the Tet Offensive on February 20, 1967. (Photo by Bettmann Archive/Getty Images)

An emu runs to escape an approaching wildfire as it burns near Potero, California, U.S. June 20, 2016. (Photo by Mike Blake/Reuters)

A Grevy’s zebra gets itself noticed at ZSL Whipsnade Zoo in Whipsnade, England on April 20, 2018. (Photo by Tony Margiocchi/Barcroft Media)